1. Field of the Invention
The invention relates to an expandable keyboard device, more particularly to an expandable keyboard device that can be used as an external keyboard of an electronic device.
2. Description of the Related Art
In recent years, due to the development of touch technology, tablet computers have gradually become popular electronic products. Although tablet computers are easy to carry, when they are placed on a desk top for use, there is lacking a support structure to keep them upright. Thus, they can only be laid flat on the desk top. This causes inconvenience for a user to view the screen.
To resolve the aforementioned problem, expandable keyboard devices are developed, apart from supporting the tablet computers upright to facilitate viewing of the screen by a user, can also facilitate the user to input messages. However, the expandable keyboard devices produced by manufacturers are suitable for use on their own tablet computers. That is, the structure for clamping and positioning the tablet computer on the expandable keyboard device is compatible only with their own product. Hence, when the user uses a tablet computer made by other manufacturer, he/she has no choice but to buy the corresponding expandable keyboard device made by said manufacturer so as to be compatible with his/her tablet computer.
An expandable keyboard device, as disclosed in U.S. Pat. No. 6,937,468, provides positioning of an electronic device, such as a tablet computer, by insertion. Apart from being used as an external keyboard of the tablet computer, it can also support the electronic device in an upright state to facilitate viewing by the user. However, the base structure for positioning of the electronic device thereto is fixed, and is not suitable for use with an electronic device having a certain thickness.